Parametric muxcover costs as per @daveshah1

diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc
index c18c3918f4130977bb89b2432ed492ad63b8b269..f43923afb628cadb2c47fba291bfd4d312aa9645 100644 (file)
--- a/techlibs/xilinx/synth_xilinx.cc
+++ b/techlibs/xilinx/synth_xilinx.cc
@@ -280,23 +280,21 @@ struct SynthXilinxPass : public ScriptPass
                        }
                        else if (widemux > 0) {
                                run("simplemap t:$mux");
-                               std::string muxcover_args = " -nodecode";
+                               constexpr int cost_mux2 = 100;
+                               std::string muxcover_args = stringf(" -nodecode -mux2=%d", cost_mux2);
                                switch (widemux) {
-                                       // NB: Cost of mux2 is 100; mux8 should cost between 3 and 4
-                                       //     of those so that 4:1 muxes and below are implemented
-                                       //     out of mux2s
-                                       case  5: muxcover_args += " -mux8=350 -mux16=400"; break;
-                                       case  6: muxcover_args += " -mux8=450 -mux16=500"; break;
-                                       case  7: muxcover_args += " -mux8=550 -mux16=600"; break;
-                                       case  8: muxcover_args += " -mux8=650 -mux16=700"; break;
-                                       case  9: muxcover_args += " -mux16=750"; break;
-                                       case 10: muxcover_args += " -mux16=850"; break;
-                                       case 11: muxcover_args += " -mux16=950"; break;
-                                       case 12: muxcover_args += " -mux16=1050"; break;
-                                       case 13: muxcover_args += " -mux16=1150"; break;
-                                       case 14: muxcover_args += " -mux16=1250"; break;
-                                       case 15: muxcover_args += " -mux16=1350"; break;
-                                       default: muxcover_args += " -mux16=1450"; break;
+                                       case  5:
+                                       case  6:
+                                       case  7:
+                                       case  8: muxcover_args += stringf(" -mux8=%d -mux16=%d", cost_mux2*(widemux-1)-1, cost_mux2*(widemux-1)); break;
+                                       case  9:
+                                       case 10:
+                                       case 11:
+                                       case 12:
+                                       case 13:
+                                       case 14:
+                                       case 15:
+                                       default: muxcover_args += stringf(" -mux16=%d", cost_mux2*(widemux-1)-1); break;
                                }
                                run("muxcover " + muxcover_args);
                        }